On the basis of a carbon isotopic record of both marine carbonates and organic matter from the Triassic-Jurassic boundary to the present, we modeled oxygen concentrations over the past 205 million years. Our analysis indicates that atmospheric oxygen approximately doubled over this period, with relatively rapid increases in the early Jurassic and the Eocene. We suggest that the overall increase...

0031-9007= The low-energy reaction 14C n; 15C provides a rare opportunity to test indirect methods for the determination of neutron capture cross sections by radioactive isotopes versus direct measurements. It is also important for various astrophysical scenarios. Currently, puzzling disagreements exist between the 14C n; 15C cross sections measured directly, determined indirectly, and calculat...

Efforts to unify group-theoretically the standard-model gauge interactions with the generation structure of fermions and their mirror partners should be accompanied with the unification of the corresponding gauge couplings. In this paper the possibility of such a unification is studied and conclusions on possible symmetry-breaking channels and scales, as well as on the fermion content of the th...

Ron Oliver is a Senior Lecture( in the Deparlnent of Library and lnfomatton Sctence at Edith Cowan Univercity, He teaches in the prc.setvice teacher education program at the Univercity. He cootdtnates the secondary teachet computet education Wogram. He is actively tnvolved in school-based research and has a paqiculat nterest in the outcones of lT programs n schools. He $ curcntly nvalved in a p...

The application of the Wilson-Sommerfeld quantum conditions to a conditionally periodic system with orthogonal coordinates involves the evaluation of an integral of the type J = f(q) dq. (1) The integral is to be extended over a.complete cycle of values of q, which oscillates between two roots of f(q). The sign of the radical is to be the same as that of dq, so that if a and b denote the roots ...

The AN−1 (2, 0) superconformal theory has an observable associated with every two-cycle in six dimensions. We make a natural guess for the commutation relations of these operators, which reduces to the commutation relations of Wilson and ’t Hooft lines in four-dimensional SU(N) N = 4 super Yang-Mills theory upon compactification on a two-torus. We then verify these commutation relations by cons...